Contact-terminal for interrupting electric circuits.



APPLICATION FILED FEB. 1, 1911.

Patented Dec. 17,1912.

, INVENTOR @aff/o- /ono/a QM M ATTORNEYS in ".the ordinary UNITED STATESPATENT OFFICE.

GOTTLDB HONOLD, 0F STUTTGART, GERMANY, ASSIGNOR TO THE FIRM OF ROBERTBOSCH, OF STUTTGART, GERMANY.

CONTACT-TERMINAL FOR INTERRUPTING ELECTRIC CIRCUITS.

Specification of Letters Patent.

Patented Dec. 17, 1912.

Apptication filed February 1, 1911. Serial No. 606,035.

scription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

This invention relates to contact terminals for interrupting electriccircuits, and more particularly to one employed in devices for ignitionof the gas mixture in combustion engines.

Upon interrupting an electric circuit there is produced attho place ofinterruption a spark having the nature of an arc, in consequence ofwhich, in cases wherein the electrical energy stored in the circuit isto be utilized at a point other than the place of interruption, a largeproportion of the energy is lost. This is especially true devices forthe ignition of the gas mixture in combustion engines wherein theinterruption of a circuit for the production of a high inductive effectat the place of ignition is employed. In fact, this difliculty is ofsuch marked degree that the formation of the spark at the place ofignition in the engine cylinder is greatly interfered with or the sparkgreatly reduced in intensity.

As tests have shown, the formation of the I are at the place ofinterruption, is due to the fact that the arc travels along theinterrupter contacts and burns the neighboring metal parts, wherebymetallic vapors are produced and deposited upon the contact surfaces ofthe interrupter, so that these surfaces become coated with the oxidizedmetal until the formation and propagation of an arc is facilitated to anextraordinary degree.

The invention consists in forming the interrupter contacts from somemetal that strongly resists oxidation, such as platinum or the like, andgiving them such shape that the path along the platinum surface from theplace of interruption to the sup porting metal of more easily oxidizablenature is as long as possible, and is preferably interrupted by one ormore sharp edges. In this manner the spark or arcforming at the place ofinterruption is prevented from reaching the more easily oxidizablemetal. In the devices of this kind heretofore used, the aredue to aninterruption formed between the edge of the contact member and theclosely adjacent support of brass or other easily oxidizable metal, inconsequence of which the brass or other metal was heated until itgenerated a vapor which coated the contact surfaces.

In the accompanying drawings forming a part of'this specification,Figures 1 to (3,

show various modifications of contact terminals constructed inaccordance with my,

invention.

In Figs. 1, 2 and 3, the contact member or head portion 6 of platinum orother metal strongly resisting oxidation is wider than the body portiona of brass or other metal of more easily oxidizable nature, in order toproduce the desired result. In this Way, the body portion is set backfrom the edge of the head portion, so that an arc must considerablylengthen in order to travel from the edge of the top portion to the bodyportion, which action is prevented by the fact that the distance betweenthe head portions of the cooperating electrodes at the place ofinterruption is materially less than the arcing distance from eitherhead portion to the support of the cooperating electrode.

The entire contact terminal may be made of platinum as in Fig. 1. Or itmay consist of a head portion 6 of platinum extending outwardly of thebody portion a of brass or the like and fastened thereto by solder orany other suitable means, as in Fig. 2. In the construction shown inFig. 3, the platinum plate (2 covers the top and side of the head ofthebody portion a of braw. According to Fig. 4, the construction is changedin such a way that the brass body portion a is inclosed by a platinumsleeve in which grooves are turned for the purpose of furtherlengthening the platinum path and preventing the passage of the are tothe support. In Figs. 5 and 6, the desired result is secured byproviding the platinum collar 6 for the raised portion of the contactsurface a. In this case the entire raised portion comprising the contactmember a and the collar 2) can be made of a solid piece of platinum asin Fig. 5; or, a properly shaped body portion a of cheap metal likebrass can be covered with a thin layer .of platinum, shaped so as toform a contact member and a protecting plate, as shown in Fig. 6. Thesame idea may be used whether the support f recedes from the contactmember 6 as indicated in Fig. 1, or whether it slides along the surfaceof the contact member as indicated in Fig. 2, to

interrupt the electric circuit. In all cases the body portion a of eachof the cooperating electrodes extends materiall away from the support sothat neither the ody portion a nor the supports f of either electrode isever traversed by the arc.

Having thus described my invention, what I claim is:

A circuit interrupting device for ignition systems for internalcombustion engines comprising relatively movable cooperating electrodesof substantially the same shape and supports therefor of more easilyoxidizable metal, each electrode having a body portion extendinmaterially away from its support, and a at head portion of metalstrongly resisting oxidation extending outwardly from the body' ortionand clear of the support and shape so that it includes a sharp edge. in"the path of an are from the place of interruption of the circuit to thesupport along-the surface of the electrode and so that the distancebetween the head portions of the cooperating electrodes at the place ofinterruption is materially less than the arcing distance from eitherhead portion to the support of the cooperating electrode. 1

In testimony whereof I affix my signature, in presence of two witnesses.

GOTTLOB HONOLD.

Witnesses MAX ANscHI'i'rz, -REINHOLD ELWERT.

